Volumetric particle streak-tracking velocimetry and its application in indoor airflow measurements

Based on existing PIV techniques and imaging principles of ordinary commercial cameras, a unique measurement method, Volumetric Particle Streak-Tracking Velocimetry (VPSTV), was successfully developed to measure all three spatial components of flow velocities simultaneously and partial-intrusively in a whole large 3-dimensional flow volume using ordinary light illumination. The VPSTV algorithm only requires two cameras to view the illuminated flow field and capture particle displacement images with the parallax effect. The technique can acquire three velocity components and flow directions in a 3-D volume, rather than a thin layer of a plane. A measurement system with associated software for indoor airflow studies was established based on the developed algorithm in a full-scale experiment room.;The VPSTV system consists of two sets of projector lamps offering volume illumination, a bubble generator seeding helium-filled soap bubbles of neutral buoyancy into the test room, two digital cameras in an angular oriented configuration with a synchronizer to trigger the two cameras, and a microcomputer with picture taking, image processing and data analysis software. The facility and hardware settings and operations, image and data processing procedures were formulated in consideration of satisfying cost-effectiveness and measurement accuracy. Methods for calibrating and validating the VPSTV system were established to improve and evaluate measurement accuracy of the system and to optimize some operating parameters with the help of theoretical analysis. Together with commercial software ImagePro Plus and Tecplot, an image and data processing software package, namely VPSTV-BEE, was developed and found to be both accurate and efficient.;The developed VPSTV system was applied in the measurements of airflow patterns and air distributions at three different levels of ventilation rate for each of two room layouts of an indoor ventilation system. This can be considered as an overall test of the system and the operating method. The airflow fields of the test cases were also simulated numerically using commercial CFD (computational fluid dynamics) software. Through a preliminary comparison between the results from the simulations and the experimental measurements, the performances of the different CFD models were evaluated.